Releasable wedge type roof bolt



Dec. 28, 1954 J. F. JOY

'RELEASABLE WEDGE TYPE ROOF BOLT Filed Oct. 1l. 1949 CLI lll

IIII

lm Ilm mi United States Patent O RELEASABLE WEDGE TYPE ROOF BOLT Joseph F. Joy, Pittsburgh, Pa., assignor to Joy Manufacturing Company, Pittsburgh, Pa., alcorporation of Penn- Sylvania Application October 11, 1949, Serial No. 120,735 fs claims. (ci. 614s) This invention relates to suspension type roof supports and more particularly to improved roof anchors insertable in holes drilled in the roof strata of an underground mine or tunnel for at least temporarily sup- Aporting the roof wholly without external supports such 'bolts may engage cross beams or plates to hold the latter in supporting position against the roofto bind the immediate strata together thereby minimizing flexure and preventing rock failure. In areas which have been worked-out it is good economy to recover the anchor bolts and to allow the roof to subside. Further, in underground workings where roof timbering is still used as in mines where uninterrupted mining is effected by continuous mining apparatus it is important to rmly support the roof near the working face andabove the continuous mining apparatus, prior to the installation of permanent timbering, and it has been found that roof bolting not only provides a reliable means of roof control for this purpose but also provides for increased roof and sidewall clearances and improved ventilation of the mine passageway. Where the roof is temporarily held up by the anchor bolts it is desirable to recover the bolts, for reuse at other locations, as the permanent `timbering is advanced. In known types of roof anchor bolts recovery of the bolts is practically impossible and in any event is extremely dangerous since the bolts must be torn loose by fracturing the roof strata surrounding the walls of the holes or by breaking up the roofv strata, due to lack of any means for releasing the expansble bolt heads.

The present invention contemplates improvements over known types of expansble anchor bolts in that the bolts are constructed so that they may be readily and quickly released from the rock strata when desired, for reuse at other locations. The anchor bolt of the present invention embodies an expansble bolt head so arranged and constructed that it may be quickly released by insertion in the hole, in the space surrounding the bolt, of a` suitable releasing instrument such as a sec- `tion of pipe, to engage and release the wedging means of the expansble bolt head. The wedging means in accordance with the present invention includes a novel wedge structure having side projections extending laterally beyond the sides of the bolt body so that the wedge releasing instrument or pipe section may be placed over the bolt body in the hole and moved into engagement with the wedge projections so that relative longitudinal movement between the wedge and the bolt 2,697,914 Patented Dec. 28, 1954 ICC An object of the present invention is to provide an improved suspension type roof support especially designed for use in supporting the roof strata of an un.` derground excavation such as a mine passageway or tunnel. Another object is to provide an improved expansible type anchor bolt so arranged and constructed that the expansble head of the bolt may be firmly secured in anchored position and may be readily released when desired. A further object is to provide an improved expansble anchor bolt having releasable wedging means for contracting the bolt head. A still further object is to provide an improved expansble anchor bolt insertable in a hole drilled in the roof strata of an underground excavation and which may be firmly anchored in position and may be quickly released when desired. Still another object is to provide an improved wedge structure for an expansble bolt head with the Wedge structure so constructed that the bolt head may be readily released by a releasing instrument insertable in the hole and engageable with the Wedge structure. Yet another object is to provide an improved releasing instrument which is held in position to eiect wedge release to contract the bolt head by the same means as that employed to tighten the bolt. A further object is to provide an improved anchor bolt which by effecting by releasing means inserted in the hole relative movement of parts of its expanded head, may enable the anchor to be readily recovered from the hole. Still a further object is to provide an improved expansble anchor bolt having an expansble head provided with a novel wedge for effecting expansion of the head, with the wedge presenting lateral shoulders or abutments engageable by a tubular member placed over the bolt for holding the wedge in stationary position during contraction of the bolt head. Another object is to provide an improved expansble head for an anchor bolt. These and other objects and advantages of the invention will, however, hereinafter more fully appear.

In the accompanying drawing there is shown for puiposes of illustration one form which the invention may assume in practice.

In this drawing:

Fig. l shows a fragmentary section of the roof strata with the improved anchor bolt secured in roof supporting position in the strata.

Fig. 2 is a view similar to Fig. l with the anchor bolt shown partially in central longitudinal section and with the wedge releasing instrument shown in wedge releasing position.

Fig. 3 is a vertical section taken on line 3-3 of Fig. 2, with a portion shown in elevation, showing the releasing instrument in engagement with the wedgeshoulders.

Fig. 4 is a cross sectional view taken on line 4-4 of Fig. 2.

Fig. 5 is an enlarged end view of the expansble head of the anchor bolt.

Fig. 6 is a perspective view showing the bolt body, the expansible split head and the expander wedge, with the wedge separated axially from the split head.

In this illustrative embodiment of the invention, as shown in the drawing, the anchor bolt is generally designated 1 and is insertable in a hole 2 drilled in the roof strata of a mine or other subterranean excavation, to hold a -roof support such as a cross beam or plate 3 in supporting position against the roof.

l` he anchor bolt comprises an elongated rodlike body 4 having formed at its upper end an expansble head 5 which, -for illustrative purposes, comprises split fingers or anchoring portions 6, 6 which are yieldable laterally. The portions 6, 6 are of semi-circular cross section and are desiiably secured by welding at 6 to the bolt body, thereby to provide a rugged construction (Fig. 2). Thus the loss `of c ross sectional strength due to slotting of a solid cylindrical piece of metal, is avoided. A wedge 7 of novel design has a central wedge portion 8 tapering downwardly and insertable between the yieldable fingers 6 as shown in Fig. 2. The wedge has parallel side portions 9, 9 formed with curved outer surfaces 10 which lie in the surface of a cylinder and are shaped substantially to fit the hole. The parallel side portions 9 of the wedge project downwardly at 11 a substantial distance below the narrow edge or apex of the wedge and extend along the "sidesof the' split'portions 6of the bolt an'd provide' 'shoulders or abutment surfaces 112 at their bottoms which project laterally from the sides of the bolt body as shown in 'Fig.'l3. .The.LyieldableY iingersvor'- anchoring portions-f6 of the expans'ible heads'lie in 'the:space-betweenf'the side'rpor- .tions'ofifthe .wedge andfhavefprongll-ikeI-'upper portionsl lnvhichr are hard faced at 13 Vto :resisttwear Aa-nd-'wl1-ich-1a-re adapted :to be embedded-i intofthewalls oftherhole. AThe lower .portion of theibolt bodyfis externallyt-hreaded#at --1'4 for-.engagement with fafnut: 15.

.In..use.the.:wedge 'f7 :is Virstplace'din= position on-the -splitzheadtof'thevanchorrbolt and'fisty then inserted bytthe -fbo-ltfintherhole and the bolt iscmovedzfupwar'dly tobri-ng the upper l end of: the '.wedge v.z ig-ainstrthe''bottom fof tithe hole,=.=and.f;then thevbolt E is-:suitfably L'drivenr'upwar'dly,`- dessirably: .with a hammering-action, to-4 cause thee -fwedge lto .deectri-'the splitfngersi lateralflytinto rmfanchoringfrelatt-ioniwithfthe walls; of the hole :asi 'shown in lFig. 1. The :cross beam or plate '.3- isithen@ placed: againstlthel'roof with .tthezlower endg-ofthe boltexten'ding "downwardly through zanxopeningil inthel-beamforfeplate. 'The nut I5 list'then 1 threaded on "the loweriendeof; the bolt :and ris. tightened yagainstf. the r :beam '.or ',plate ik to yasecurefthe '2 :latter 4dirrnly Ein :supporting position :againstithe roof. When it-is desired 1' toreiect release ofytheianchorrbolt thel nut'andbeam-or :plate maybe removed from"` the bolt.- and: af tubular "releasving-.instrument 17-fdesirably;inltheform of a @pipe section ',maynbefinsertedzintheiholetfoutside ofz the bolt body and the; beam or plate r3; and nut 15 4may thenfbeL'replacedf-so -that1 the lower end of'l the 1 piper section I rests: on` the'fbeam .or.;plateas`shown in'Fig. 2y and-.with the upper` end of the :pipe section engagingi the 1 shoulders i12 v'at thebottom of tthefwedge asfshown in Fig. 3. '.Thenutfmay then be again :tightened toetfect drawing "offtheibolt bodyan'df'bolt `head .downwardlywhile the wedgexisheldwup instationary :position against the holei'bottomfby'the pipetsection or, .if there is^initial separation :between the anchor and Athe bottom of the hole,:and'if the length of theinstrument-17 isVl such. that itv is placed under :compression i before :the plate .3 Vengages the roof,: to .movefzthetwedgerasslightdisstance upwardly `intofenga'gement withrthehole fbottom priort to drawingdown of thetboltbody; and asthewedge v is f moved t upwardly-or .as theibolt .is r drawnldownwardly the spring fingers 6 are contracted to .the1position1shown in Fig. 2, out of contact with the hole-Walls. .Theuanchor land roof support rnaythen'befremovedtrom I'the-roof .strata for-reuse at another location. '-Withreferenceto the release of the roof bolt fromzthe holezitfw-ill be apparent that bythe provision-ofthe pipe-"sectionbetween :the nut yon the bolt andt the Y shoulders. 1.2.-'onf the wedge, the pipe .section 17 .upon .screwingtofi they nut towards=the split end of the bolt, will eect relative longitudinah movement ybetween` the .wedge andthesplit'endf of the-bolt, so .itis immaterial whether .the boltinitiallyfmoves outwardly .relative to-the stationary-:wedge :or whetherwthe wedge,

as might be possible if it were not in engagementfwith' the hole bottom` inthe expanded ttpositionfof ithe roofbolt, moves inwardly relative to the momentarily stationary :bolt. Rathercertainly most .oftthexcollapsingoffthe bolt head will be accomplished by movementzof the'rbolt downwardly-with respectnto:ther/wedge. What is necessary in .such contraction of thebolttheadfistto effe'ctrrelative longitudinal displacement between .the wedge and Lthe -tlater- --allybent ends of the split'boltzh'ead.sotthattthere-fmay be space for these bentvends to approach:eachwotherrsui- -ciently to allow their `withdrawalfromgtheihole. Iflthere .is suiicientspacefor the wedgefto; move vinwardly-sli'gl'rtfly .toward the hole bottom while:the:boltfremains'stationary with its bent end portionsgzembeddedfinrthe .'holeawalls, 'the establishment of a clearance between the bent bolt ends k6 and the wedge can be very readily initiated. .Whether or-not, however, this is possible'is immaterial be- .cause the recesses inthewall of the hole .engaged by the ends 6 of the bolt can never have their wallsspaced from the adjacent points oftthe wedge surfaceiof the'wedge .element by lesser distances than'the thicknesses of the spaced ends. Thus, if the-'wedge be heldstationary and there be an outward movement of theboltzrelativeltolthe stationary wedge, therewill be'no such interlock with the wall of the hole vso .as -to prevent concurrent .outward movementof the bolt and mutual approach 'of its split ends. `Whether the element 3is vemploye'cltor'n'ot during .withdrawal of the bolt is alsoimmaterial. v.If'it is,tafter .the spaced -ends of kthe-bolt havefbeentzbrought partially .together within the bore of fthepipe ysection`t17 arrdlthus `inglyaevfident that. by the provisionoffthe tshouldersson the wedge 'designed for. engagementwiththe releasing instrument the anchor bolt may be readily and .quickly released.

As a tresultuof this invention 'xanfimprovedtsuspension type roof support for mines or other subterranean excavations is providedtwhich may'f'not only be firmly anchored in place in a hole drilled in the roof strata but which may also be readily and quickly released when "deSired. rPhe expansibletanchorbolt; byithefprovision of fthe :improved mve'dge tstructure, ltmay tbe 2 readily treleased simply by pla'cingffa.l suitable: releasing-instrument:against shoulderseprovidedfby .thefwedgerso thattthe wedgmmay .be .held stationary in. the .,hole \while the .bolt is -ldrawn xdownfvardly'.or the? wedge.- may bein-loved.upwardly-While the bolt is momentarily stationary,=.to.eiect-releaselof .its.expansible head. Thus. by relatively;movingfthetsplit :head .fand-.wedge, the.anchor. may betreadilyt released. .-'By `the provision .of the novel. structure disel'osedaroofaanchor `.ofetheftype-Which normally remains penrnanentlyfinnthe yrock strat-a fwith l but ismall fmodicat-ion fmay :be made 'readily releasable, thereby, enabling rreuse, of. the :anchor fas desired. .By. formingt the-.expansible headiof the f bolt by weldingr =a .pain .of semi-.circulariparts totthebolty body .-and .by t providing the poi-nts of the expansible @portions fwith. hardsfacingfnot-.onlyi is .the-,cross .-sectionli strength .oft thetbolt-head materially increased -.but':also resistance to wear .is improved. fhesevandtother t manners ftuse .and'advantages-oft the invent-iontwilltbe..clearly fapparent 5to4 those skilled` inzthe art.

While; there is.A in `thisfapplication-.v speciically. :described 4.one :form Vlwhich .the :invention tmay assume infpractice, .it will. be. understoodA .thattthis formt ofthe-:same isrshown for purposes of illustration, I land that .-.the .invention i may A.be-.modified .and embodied variousothervforms fwith- :glut departingffroml its-.spirittonthe scopeI of the appended alInS.

n '-.WhatI claimas.new..and\desirei.totsecure by Letters .Patentiisr A tl. releasing-.device tor releasingta.` releasable f anchor .,bolt, of,.'the .kind..insertable. in aahole of substantial .depth 'formedfinwstratato bey supported comprisingaanrelongated .boltfbody of .smaller cross .sectional area than f the hole .thereby `leaving-.a.spacerbetweentthe exterior ofnthe b0lt bodyeand. the `.hole-walls, :said bolt-body :carrying: an t ex- .pansible Lhead 1 at its inner ,end, .-iand. a wedgerengageable withfthelhole bottom,.saidwedge-and said\.bolt head being relatively movable to effect expansion.f.ofrsaid.headfinto .engagement withal-1e,holefwalls-.to :anchori: said-rboltfinf the strata, said rwedgehaving atlateral u projection :extending `outwardly beyond t .one #side f of tfsaid .bolt body :into said space.fand.providing antabutment shoulder adaptedzfor engagement .by-.a releasing rinstnument, :said releasing .de vice comprising .a releasing zinstrum'ent linserta'ble in tsaldgspacei'within theholeeexteriorlytof the boltlbo'dy .into engagement -.with said rwedgeprojection Aand coop- .eratin :with: saidtbolt ttoieiectl'relative-fmovementof `vsaid .wedge and J-bead .fior ffeiiecting :scontraction f `said head wherebyzsaidbolttmay be readilyfrernove'difromftheihole. .2.v A releasing 7device/as setfforthiin `claim lliwherein the wed'gefof lsaid \-anchor-bolt1 hasfatits/ outer "endoppose'd later-al aprojections extending into 4'said "space within .the vhole aandjj'provitling .outwardly 'facingv 'abutment ishoulvders and said releasingf instrument Iis in :fthe [form of a ytube :insertabl'e in `the Thle .over tsaid bolt in the :space `surrounding the lbltbody .and .ab its Linneriend .engaging .said abutment.shoulders1 for: effecting-such.relative movement .of .said wedge;.and .head

.3. `A :releasing device .for .a treleasable;fanchor bolt Vas setforth-l-inaclaim ZfWhereinstherwedgexofisaidrfanchor .boltt comprisesav central wedge-shaped poi'tion'farrdl parl- .lel side arms.f.project-ing=:from "sid twedgexshapedpor'tion 'asubstantialLdistancefoutwardly othe yapexfo' said wedge, fsidesidezarms-have fcurvedf exteriorssuffaces-lyingy within a circle and substantially tting the hole-walls, and said projecting side arms also have abutment surfaces at their outer ends with which the inner end of said tube engages.

4. A releasing device for releasing an expansible type anchor bolt of the kind comprising a bolt body insertable in a hole in strata to be supported and of smaller cross sectional area than the hole to leave a space between the exterior of said bolt body and the hole-walls, said bolt-body carrying an expansible head at its inner end, a wedge engageable with the hole bottom and cooperating with said head to eiect expansion thereof, and tensioning means for said bolt acting on the outer surface of the strata to effect binding of the strata together in supported relation, said wedge having a lateral projection extending outwardly beyond one side of said boltbody into said space within the hole and providing an abutment surface, and a releasing instrument insertable in the hole in said space exteriorly of the bolt body and engaging said abutment surface on said wedge and cooperating with said bolt tensioning means to eiect contraction of said head whereby said bolt may be readily removed from the hole.

5. A releasing device as set forth in claim 4 wherein said bolt tensioning means engages a plate placed against the outer surface of the strata and said releasing instrument is disposed between said plate and said abutment surface on said wedge whereby when said tensioning means is adjusted to draw the bolt axially outwardly within the hole, said releasing instrument holds said wedged against movement so that said head may be contracte References Cited in the tile of this patent UNITED STATES PATENTS Number Name Date 268,207 Edmonds Nov. 28, 1882 531,363 Dinkelacker Dec. 25, 18.94 642,066 Bargelt Jan. 30, 190() 710,216 Schmidt Sept. 30, 1902 1,180,572 Cox Apr. 25, 1916 1,496,134 Rumgay June 3, 1924 1,746,050 Phillips Feb. 4, 1930 1,841,190 Justiss Jan. 12, 1932 2,587,907 Schroeder et al. Mar. 4, 1952 OTHER REFERENCES Engineering and Mining Journal, May 1943. 

